1. Field of the Invention
The invention relates to a method of producing monocrystalline layers on a substrate in somewhat more particularly to a method of producing monocrystalline structured layers on a substrate surface.
2. Prior Art
In semiconductor technology, semiconductors are required which have a periodic superstructure in a surface thereof wherein the distance between the periods of such structures is larger than or is a multiple of a lattice constant of the semiconductor. Further examples wherein semiconductors having select structures in a surface thereof may be found in laser technology, for example, in tuning of solid-state lasers and light waveguides. Such structured semiconductor layers are also required in the production of other components wherein, for example, monocrystalline polycrystalline regions or zones or heterogeneous monocrystalline zones are positioned in close proximity to one another. A method for producing such structured semiconductor layers is, for example, described in an article appearing in "IEEE Transactions on Electronic Devices", Vol. ED-18 (1971), pages 45-49. In this method, which is sometimes referred to as "selective epitaxy deposition", narrow areas or zones having a monocrystalline structure and similar interposed areas having a polycrystalline structure are formed in a semiconductor layer by epitaxy deposition. In this process, individual areas having polycrystalline structure are positioned via a photo-lithographic technique onto a surface of a monocrystalline substrate and an epitaxial deposition is then performed. Material in polycrystalline form is deposited on those areas of the substrate surface on which the polycrystalline "seed" material is present and material in monocrystalline form is deposited on those areas of the substrate surface which are not covered with the polycrystalline seed material, i.e. those areas which are monocrystalline. The minimum spacing between two monocrystalline areas or zones so-produced is dependent upon a number of factors, for example on how sharp or precise of an image of the photomask is transmitted to the photo resist, the degree of edge under-etching that occurs during the development of the exposed photo resist, etc. Accordingly, this "selective epitaxy deposition" process cannot be utilized to produce structures having dimensions smaller than about 0.5 .mu.m. Further, this prior art method is unsuitable for depositing strips of monocrystalline material onto an amorphous substrate.